Integrated circuits have evolved into complex devices that include multiple levels of metal layers to electrically interconnect discrete layers of semiconductor devices on a single semiconductor chip. Recently, with the evolution of higher integration and higher density of integrated circuit components, the demand for greater speed of the data transfer rate is required. For this reason, an insulating film having low leakage current, low dielectric constant to give the small RC delay is employed.
As the dimensions of the integrated circuit components are becoming increasingly denser, the materials used to fabricate such components contribute to the electrical performance of such components. One way to reduce the size of interconnection lines and vias is to change the wiring materials from the conventional aluminum (Al) to copper (Cu) wiring having low electric resistance.
However, to produce a semiconductor device having multi-layered copper wiring, a low dielectric constant insulating layer is formed as the interlayer insulating film on the copper wiring.
Furthermore, the use of copper as the interconnect material has various problems. For example, copper is easily diffused into the low dielectric constant insulating film from the copper wiring, thus increasing the leakage current between the upper and lower wiring.
The use of silicon carbide films as copper diffusion barrier layers has been published in U.S. Pat. No. 5,800,878. The dielectric constant of this film is such as about 5, and in addition it is used as copper diffusion barrier layers for 130 nm-nodes Large Scale Integration (LSI) technologies where the dielectric constant of the interlayer dielectric film is 3.
For next generation, 100 nm/65 nm-nodes Ultra Large Scale Integration (ULSI) technologies, the reduction of interconnect capacitance is important for suppressing the signal delay as well as the power consumption. Interlayer dielectric films with dielectric constant less than 2.5 are used with copper damascene structures. To decrease the effective dielectric of fine pitched lines, further reduction in the dielectric constant is necessary not only for the inter layer dielectric film itself but also the supporting dielectric films such as hard mask, etch stop layers and copper diffusion barrier layers. Furthermore, to prevent the migration of metal atoms the leakage current of such film at 1 MV/cm has to be less than that of 1×10−8 A/cm2. Silicon carbide films with dielectric constant less than 4.5 such that the leakage current at 1 MV/cm is less than 1×10−8 A/cm2 are suggested to be suitable to substitute for as such films.
The method of forming Nitrogen doped silicon carbides (SiCN), oxygen doped silicon carbides (SiCO) has been published in U.S. Patent Application Publication 2001/0030369, U.S. Patent Application Publication 2002/0027286, U.S. Patent Application Publication 2001/0051445, and U.S. Patent Application Publication 2001/0031563. Furthermore; these films have been proposed as copper diffusion barrier layers. Though a nitrogen doped silicon carbide layer has been proposed as a copper diffusion barrier layer with low leakage current, its dielectric constant is 4.5 to 5.0 and this results in significant increases in the effective dielectric of the total dielectric stacks.
In case of oxygen doped silicon carbide, although its dielectric constant is relatively low, such as less than 5, it cannot sufficiently refrain from increasing the leakage current. To decrease the leakage current to a sufficient level, the oxygen must be introduced much more into the silicon carbide film.
However, to do so, the leakage current can be reduced up to a satisfactory level, nevertheless a new problem is caused such that the surface of the copper wiring is oxidized and thus the barrier insulating film and the inter dielectric layer is ready to peel.
Silicon carbide has also been suggested for use of barrier layer on integrated circuits, since silicon carbides can have a low dielectric constant.
However, the dielectric constant and stress of the conventional silicon carbide film drifts when it is directly exposed to air. This is due to the oxidation of the top surface of the silicon carbide film. The method to minimize the oxidation of carbon containing materials, such as silicon carbide, with an inert gas plasma such as helium (He), Argon (Ar) is published in U.S. Patent Application Publication 2001/0060584. This inert gas plasma treatment only minimizes the top surface of the silicon carbide film from getting oxidized, however, no changes/improvements to the film properties are observed.
Furthermore, although the dielectric constant is relatively low, such as 4.0, the conventional SiC barrier insulating film cannot sufficiently suppress the increase in the leakage current. In this case, to enough suppress the leakage current, a new method is desired that can produce a barrier layer that is effective in preventing the migration of metal atoms while also exhibiting low dielectric constant and low leakage current.